Research On Key Techniques Of Channel Estimation Of MIMO-OFDM System

Nowadays, the 4^th generation mobile communications, which base on the MIMO-OFDM technology, has emerged just shortly after several decades' development of wireless and personal conununication, which has burgeoned from analog to digital and from FDMA to CDMA. It is an integrated communication system including broadband, Internet access and many other integrated functions. Now, China's Future Technology for Universal Radio Environment (FUTURE) project and Europe's Wireless World Initiative New Radio (WINNER) project also accept MIMO-OFDM as the base of physical layer.In the first chapter, the progress of the mobile communications is reviewed. The current progress of 3G,B3G/4G is introduced. The key techniques and the problems lying in B3G/4G are denoted.In the second chapter we introduced the principle of OFDM and MIMO and the structure and principle of MIMO-OFDM system at first. Secondly, introduced the characteristic of the wireless mobile channel in mobile communication, and the fading effect caused. Then analyzed the model of the wireless channel and then simulated it. And a real MIMO-OFDM system was shown in the last part.In the third chapter, the channel estimation in MIMO-OFDM systems is investigated initially. The Mean Square Error (MSE) bound of various interpolations is derived and verified by simulation.In the fourth chapter, we propose three different channel estimation algorithms based on specially designed comb type pilots inserted in frequency domain. One of our proposed algorithms is performed in frequency domain and the other two are performed in time domain. Such comb type pilot based algorithms can provide higher bandwidth efficiency than common significant-tap-catching algorithm using training block pilots. Numerical analyzes and computational simulation show that our proposed estimation schemes have the same good performance while the time domain methods have relatively simple structure.In the fifth chapter, we provides a new technique to mitigate the clipping noise on pilot symbols in MIMO-OFDM systems. The basic principle is to directly filter the clipping noise on the positions of pilots in the frequency domain before the insertion of pilots .Simulation results show that the new technique can effectively improve channel estimation and system performance.At last, conclusions are remarked and the possible research issues in B3G/4G are shown.